FIG. 1 illustrates schematically a cross-section view of a natural eye (1) such as a human eye. The eye includes a cornea (2), an iris (3), a lens (4) defining a central optical axis (5), a ciliary sulcus (6) connected to the lens by a zonal ligament (7), a retina (8) with a macula (9) at its central region centred upon a fovea (10) where the central axis (5) of the lens intersects the retina. An anterior sac (11) is bounded by the cornea and the iris. A posterior sac (12) is bounded by the iris and the retina, and contains the lens.
Light rays (not shown) parallel to the central axis of the lens and incident upon the cornea are able to be focussed by the refractive poser of the cornea and lens incident upon the macula at the fovea of the eye. Light rays striking the cornea obliquely are unfocussed and provide less acute, peripheral vision.
Degeneration or damage of the retina at the macula (known as macular degeneration) reduces the ability of the retina to detect light incident there. This greatly reduces visual acuity by degenerating those regions of the retina upon which the eye is arranged to form focussed images. Such degeneration typically results in a blurred spot or dark spot forming at the centre of vision where, prior to degeneration, a focussed image would be. Peripheral vision remains largely unaffected.